Influence of natural selection on the reproductive function in bulls

V. I. Petrenko, V. I. Barabash
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Institute of Grain Crops NAAS, 14 Volodymyra Velykoho str., Dnipro, 49027, Ukraine

The article presents long-term research results on the impact of natural and sexual selection on the reproductive function in bulls under tethered and loose housing conditions. It was found that dominant males within the herd hierarchy have preferential access to resources and mates, resulting in decreased libido, semen quality, and reproductive activity in subordinate bulls. Rank-related stress is identified as a key factor causing impotence and reproductive failure in these animals. Dominant individuals demonstrated superior adaptability, higher sperm production, and neurotypical characteristics associated with leadership. A comprehensive assessment of physiological, ethological, biochemical, and morphological parameters revealed effective strategies for improving housing conditions, mitigating the impact of intrasexual selection, and stabilizing reproductive function in breeding herds. For the first time, the type of higher nervous activity in bulls is proposed as a selection criterion for forming a high-performance breeding stock. The findings are crucial for refining bull management, selection, and application in artificial insemination and genetic improvement programs.

Keywords: bulls, natural selection, sexual function, rank stress, herd hierarchy